1. Technical Field
This invention relates to bumper systems and, more particularly, to bumper systems for use with automatically controlled, self-propelled vehicles to prevent damage to the vehicle and other obstacles.
2. Background Art
Self-propelled, automatically controlled vehicles are used in business environments to provide mail delivery and similar functions. The structure and operation of such vehicles are disclosed in Cooper, U.S. Pat. No. 4,042,058 issued Aug. 16, 1977, and Houskamp et al, U.S. Pat. No. 4,020,918 issued May 3, 1977. The vehicles described therein are automatically controlled to follow a guide path in a predetermined manner. However, there exists a finite probability of collisions between vehicles and various obstacles, especially with several vehicles simultaneously operating on one guide path within an industrial or similar environment. Therefore, these vehicles often include bumper assemblies to minimize the effects of a collision and to indicate to various vehicle control components the occurrence of a collision.
The bumper assemblies disclosed in the aforementioned patents include a bumper and pressure sensitive switches to stop the vehicle when it collides with an obstacle in its path. Other prior art bumper assemblies also mechanically activate circuits and/or switches mounted directly to the bumper or vehicle frame, thereby causing a closure or opening of a conductive path interconnected with a vehicle power system which, in turn, causes the vehicle to decelerate. For example, as disclosed in Satterfield, U.S. Pat. No. 3,599,744, issued Aug. 17, 1971, a vehicle safety device comprises a foam bumper mounted to a pair of bumper frames connected to a vehicle frame by hinge pins. The bumper frames pivot about the hinge pins upon impact, thereby causing a switch mounted on the frame to be opened and the vehicle power system to be disengaged.
In Vaill, U.S. Pat. No. 4,126,344, issued Nov. 21, 1978, a bumper system is supported on a vehicle with springs and levers pivotably mounted between the bumper and the vehicle. When the bumper impacts with an obstacle, the springs and levers activate a power switch which stops the vehicle.
Jennings et al. U.S. Pat. No. 4,137,984, issued Feb. 6, 1979, discloses a self-guided load transporter having a bumper made of plastic tubing mounted to the transporter by cables, pulleys and springs. A motor deactivating switch mounted on the transporter frame is activated by an arm when the bumper strikes an obstacle.